This invention relates in general to electrical submersible well pump motors, and in particular to debris seals to protect electrical connectors.
Electrical submersible well pumps are often employed in low pressure oil wells that produce large amounts of water along with the oil. The pump assembly is typically suspended on a string of production tubing within casing. Normally, the pump is located at the upper end of the assembly and connects to an electrical motor assembly at the lower end of the pump. A seal section locates between the motor and the pump for equalizing the pressure of dielectric liquid in the motor with hydrostatic pressure in the well.
An electrical connection receptacle is located near the upper end of the motor. A power cable extends from the surface into the well. The power cable has a motor lead on its lower end that releasably connects to the receptacle. In some cases, due to the size of the pump, tandem motors will be used. The upper tandem motor has a base or adapter on its lower end that connects to an adapter on the upper end of the lower tandem motor. Wires from the upper tandem motor lead to electrical connectors in the adapter of the upper tandem motor. These electrical connectors engage electrical connectors on the upper end of the lower motor. The motors are filled with the dielectric liquid or lubricant, and the interiors of the motors are in fluid communication with each other.
Submersible motors typically use bronze bushings and bearing sleeves that produce metallic debris from normal wear over time. Metallic debris will sometimes migrate through the dielectric oil and lodge around and inside the open spaces of the electrical connectors. This can cause a phase-to-phase or phase to-to-ground short, thus destroying the motors. Also, it is possible for small amounts of water or moisture to migrate to the electrical connectors, creating a short.
The motor assembly of this invention has an electrical connector assembly with an insulator having a passage. An electrical conductor having an insulation layer on its exterior extends extending from the motor into the passage of the insulator. The passage has an inner diameter that is larger than an outer diameter of the insulation layer, defining an annular cavity between the insulation layer and the inner diameter of the passage. An electrical connector is joined to the electrical conductor within the passage.
An elastomeric debris seal is positioned around the insulation layer. The debris seal has a final size in which it seals around the insulation layer and blocks entry of debris into the annular cavity. The debris seal is of a material that swells upon contact with a dielectric fluid and has an having an initial size in which it does not seal the annular cavity to enable the dielectric fluid to flow into the annular cavity prior to the debris seal reaching the final size.
The operator fills the motor by drawing a vacuum, then introducing dielectric oil. The dielectric oil initially flows past the debris seal to fill the annular cavity surrounding the insulation layer. Then over time, the seal will swell to seal the cavity to prevent the entry of debris.
In the embodiment shown, the motor assembly is a tandem motor assembly. The upper tandem motor has a plurality of wires that extend downward to upper electrical connectors in an upper adapter. Similarly, the lower motor has wires that extend upward to lower electrical connectors at the upper end of a lower adapter. An elastomeric debris seal locates in the upper adapter passage that surrounds each wire. The upper adapter debris seal seals around the upper wire in each upper adapter passage to prevent debris from collecting around the upper electrical connector.
In the preferred embodiment, each adapter wire passage has an insulator located within it. The insulator in the upper adapter passage has one of the debris seals located above it to prevent entry of debris between the inner diameter of the insulator and the wire. The insulator of the lower adapter electrical connector engages the insulator of the upper adapter in a sliding overlapping engagement. Another debris seal locates in the overlapping walls of the insulators. This debris seal prevents debris from migrating into contact with the electrical connectors of the lower motor.